After the CREATE_CHILD_SA exchanges, three IKE_SAs exist between
A and B; the one containing the lowest nonce inherits the CHILD_SAs.

It should say:

After the CREATE_CHILD_SA exchanges, three IKE_SAs exist between
A and B; of the two new IKE_SAs, the one containing the lowest nonce
is redundant and will be closed; the other one inherits the CHILD_SAs.